Jeep Strokers

IDK if this helps but when I ported my head I used my dremel to basically clean up all the ruff edges in the combustion chamber, as well as the intake, exhaust runner and valve seats. I don't have a picture with the gasket on the head but the intakes match the the gasket while the exhaust was just cleaned up and smoothed. If you going to do this, wear a face mask and goggles. I swear I've been blowing head dust out of my noes for weeks. I also had to use a Q tip to remove a peice of metal that was impeded into my eye. here are some pictures

You did a much better job than most, and yes, you can blow some chunks if you don't use a respirator.
John

aaronkeiser wrote: I also had to use a Q tip to remove a peice of metal that was impeded into my eye.

safety glasses was a great invention.
nice job on the head.

what did you use to paint the intake and what did you do to prep? how has it held up if you are already running it?

Well the head was taken from a junkyard 91 xj so its the better 7120 head. it was in ruff shape since it had 230,000 miles with possibly a new head gasket. The exhaust runners had a big layer of black crap which narrowed the runner by almost 1/4 in. I gave it to my local machine shop where they ran it through their parts washer and sandblasted the combustion chambers and exhaust ports to get down to bare metal. This is my first port ever but from reading the stroker emails it gave me an idea of how to do it. As far as the intake goes in the last picture It came from ebay and I gave it some soap and water to freshen it up. This head is sitting in the garage since im waiting for my block to come back from the machine shop. By the way I was wearing safety glasses but a piece fell on my eyelash. Then I rubbed my eye later that night which made it fall into my eye and stick.

tigerShark wrote:would you clean up the protrusions below the fuel injector holes in the intake?

Good question, it's amazing how this type of stuff never comes up on the email list. As you know the injector bosses have differing sizes inside the runner. They (not coincidentally) are smallest on Cylinder 1 and 6 and biggest in the middle. Also the two middle runners have a very pronounced bump on the runner wall.


All the 99+ intakes I've seen have this and I've never seen a 99+ intake with anything close to noticeable core shift in the casting. So this isn't sloppy casting, as I've seen some people suggest. This is a modern precision casting almost certainly CAD designed and highly optimised. The thicker bosses and protrusions are there to equalize air flow across the runners... and in the case of the thicker bosses keep the faster moving air from shearing the injector stream into the roof of the port. The outlying runners (1 and 6) are furthest from the TB. The inside (3 and 4) have another deliberate design features to lower their air flow... they take an extra turn (slightly s curved).

Personally I plan to knife edge the 1 & 6 injector boss, and take the same amount off the others. Leaving about 1/8th on 3 & 4 and a 16th on 2 & 5... I haven't decided if I will mess with the big bump in 4 & 5.

Equal flow is a good thing from what I understand, although how important it truely is to maximizing power output I don't know. Maybe Flash knows the theory behind it? It's almost certainly good for durability.

can an intake be tested on a flow bench like heads can?

sure there are all sorts of ways to couple things on a flow bench. The interface is pretty simple stuff, basically like a gasketed vacuum attachment, usually it's a cylinder shape to mate to the bottom of a head.

You can make a ghetto fab flow bench from a vacuum, some clear tubing, a beaker of colored water and some RTV silicone to form a plug. Of course the numbers will only have meaning in relation to your own numbers unless you learn how to calibrate the setup like a standard flow bench. But you can compare the inches of water the vacuum pulled on your own stuff.

Here are some of my port work... i cant totaly figure which is the finished, since i havn't sorted the pics... hope this helps someone, what i mainly did was this:

1. gasket match the intake ports to the gasket and match the intake itself to the gasket (then a 4.2L intake, now 92YJ
intake). finished off with an 80 grit sandpaper.

2. enlarge a bit (as per dino's advice and measurements) the exhaust ports and smooth them out to mirror like finish, for
stopping the carbon build up.

3. smooth the chambers to mirror like finish, for stopping the carbon build up.

4. short side radius, was mainly grinding protrusions inside the ports short side, i dont have many pics of the procces, but it has mentions on various locations on the web,

here are some pics...

before any work:
the intake port, and the gasket matched.
smoothed out exhaust port

more pics,

finished combustion chambers, all smoothed out and CC'd (matched to one another at 58.5 cc)
after blocking the water passages to fit the 4.2 block. i used ProPoxiy, which is like JB weld, just not liquid but solid
modelling clay mixed together, then sanded it out using very fine sand paper to match the head surface.
an overall picture of the head after intake matching it (i think, not sure what stage it was).

another 3 pics:

assembling the exhaust manifold, it was a little warped but i managed...
another closer pic, notice the gasket matched intake ports:
another pic of the matched intake ports:

last pic:

finished chamber, notice the spark plug orientation.
the plug itself point out to the intake valve... i read somewhere on the list , or on Jeeps Unlimited that pointing the spark plugs to the intake ports helps out maximazing the mixture burn, dont know if its true since i tried so many mod's at one run (new 4.0L head, new cam, ported head and so on and so...).

Lots of good info here.

I'm going to use the 99+ intake. As noted eariler in the thread, the intake runner opening is smaller than the intake head port. Also I checked this with my gasket. So I am thinking that it makes sense to port match, not gasket match, the intake to the head. Head work would be limited to misc. clean up, not gasket match. Seems like a smooth transition from the intake to the head is better than an abrupt end/change in area at the intake/head interface. Thoughts?

I don't suppose anyone here knows what those little dimples in the combustion chambers oposite of the spark plug holes are? It might be easy to assume that it's a casting iregularity common to all 258 and 4.0 heads (they all have it at least from the 80's onward) but there's no reason I can think of why there would need to be any iregularity there, so it must be designed in...

They do impair a nice swirl..........
John

He this is a hell of a bump...but I had the same question. That protrusion across from the spark plug, can it just ground out? See,a to serve no purpose?

Also the odd shape to the chamber..can it be changed a bit? Like the wider "bell" by the intake valve, which then necks down on the exhaust side..why not make it even, or less pronounced at least?

I sure wish 1bolt were still around I have some many questionse